Cyclic Aminophosphites and -phosphoranes Possessing Six- and

N. Satish Kumar, K. Praveen Kumar, K. V. P. Pavan Kumar, Praveen Kommana, Jagadese J. Vittal, and K. C. Kumara Swamy. The Journal of Organic Chemistry...
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Inorg. Chem. 1997, 36, 2044-2051

Cyclic Aminophosphites and -phosphoranes Possessing Six- and Higher-Membered Rings: A Comparative Study of Structure and Reactivity Musa A. Said,† Melanie Pu1 lm,‡ R. Herbst-Irmer,*,‡ and K. C. Kumara Swamy*,† School of Chemistry, University of Hyderabad, Hyderabad-500046 A.P., India, and Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4, D-37077 Go¨ttingen, Germany ReceiVed October 1, 1996X

Aminophosphoranes 2 and 4-9 with a cyclohexylamino substituent and ring sizes varying from five to eight have been synthesized by oxidative addition reactions of cyclic aminophosphites with diols or 1,2-diketones. The reactivities of these phosphoranes are compared with those of the corresponding cyclic aminophosphites. The difference in hydrolytic pathways between amino- and analogous phenoxyphosphoranes is discussed. X-ray structures of two sets of compounds, (a) (C6H11NH)P(OCH2CMe2CH2O) (1) and (C6H11NH)P(OCH2CMe2CH2O)(1,2-O2C6Cl4) (2) and (b) (C6H11NH)P{O-(t-Bu)2C6H2)2CH2} (3) and (C6H11NH)P{(O-(t-Bu)2C6H2)2CH2}(1,2-O2C6H4)‚1/2Et2O (4‚1/2Et2O) have been determined and geometrical parameters compared between the P(III) and the corresponding P(V) compounds. In 1, the six-membered ring has a chair conformation with the amino group axial; in 2, the six-membered ring is located apical-equatorial in a trigonal bipyramidal geometry and has a boat conformation. The eight-membered ring has a boat-chair conformation in 3, whereas the same ring has a tub conformation in 4.

Introduction Cyclic oxyphosphoranes in which the pentacoordinated phosphorus is part of a six- or higher-membered ring have been the subject of intensive structural investigations during the past few years.1-5 Structural studies on the corresponding cyclic phosphites, particularly those with a 1,3,2-dioxaphosphorinane ring, have been mainly limited to the solution state,6 except for one important study by Verkade and co-workers.7 Normally, a change in conformation occurs for the 1,3,2-dioxaphospho†

University of Hyderabad. Universita¨t Go¨ttingen (X-ray). X Abstract published in AdVance ACS Abstracts, April 1, 1997. (1) (a) Bentrude, W. G. In Phosphorus-31 NMRsSpectral Properties in Compound Characterization and Structural Analysis; Quin, L. D., Verkade, J. G., Eds.; VCH: New York, 1994; Chapter 4. (b) Yu, J. H.; Arif, A. M.; Bentrude, W. G. J. Am. Chem. Soc. 1990, 112, 7451. (c) Yu, J. H.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. J. Org. Chem. 1990, 55, 3444. (d) Broeders, N. L. H. L.; Koole, L. H.; Buck, H. M. J. Am. Chem. Soc. 1990, 112, 7475. (2) (a) Holmes, R. R.; Kumara Swamy, K. C.; Holmes, J. M.; Day, R. O. Inorg. Chem. 1991, 30, 1052. (b) Prakasha, T. K.; Day, R. O.; Holmes, R. R. J. Am. Chem. Soc. 1994, 116, 8095. (3) (a) Burton, S. D.; Kumara Swamy, K. C.; Holmes, J. M.; Day, R. O.; Holmes, R. R. J. Am. Chem. Soc. 1990, 112, 6104. (b) Kumara Swamy, K. C.; Day, R. O.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1990, 112, 6095. (c) Prakasha, T. K.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1992, 31, 725. (d) Prakasha, T. K.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1992, 31, 1913. (e) Prakasha, T. K.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1992, 31, 3391. (f) Prakasha, T. K.; Burton, S. D.; Day, R. O.; Holmes, J. M.; Holmes, R. R. Inorg. Chem. 1992, 31, 5494. (g) Prakasha, T. K.; Chandrasekaran, A.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1995, 34, 1243. (4) Hans, J.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1992, 31, 1279. (5) (a) Day, R. O.; Kumara Swamy, K. C.; Fairchild, L.; Holmes, J. M.; Holmes, R. R. J. Am. Chem. Soc. 1991, 113, 1627. (b) Hans, J.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1991, 30, 3928. (6) (a) Maryanoff, B. E.; Huchins, R. O.; Maryanoff, C. A. Top. Stereochem. 1979, 11, 187. (b) Gallagher, M. J. In Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J. G., Quin, L. D., Eds.; VCH: Deerfield Beach, FL, 1987; Chapter 9. (c) Bentrude, W. G.; Setzer, W. N. In Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J. G., Quin, L. D., Eds.; VCH: Deerfield Beach, 1987; Chapter 11 and references cited therein. (7) Schiff, D. E.; Richardson, J. W., Jr.; Jacobson, R. A.; Cowley, A. H.; Lasch, J.; Verkade, J. G. Inorg. Chem. 1984, 23, 3373. ‡

S0020-1669(96)01195-0 CCC: $14.00

rinane ring from a chair in the tricoordinated cyclic phosphite (I, solution state studies6) to a boat/twist in the pentacoordinated phosphorane (II, solid and solution state studies1-4). The

presence of H-bonding as in III can reduce the relatively small energy difference between the chair and boat conformations;5 in fact, when R ) H and Ar ) Me2C6H2O, a chair conformation was observed for the phosphorinane ring.8 In this connection,

an aspect worth looking into is to introduce H-bonding into the phosphorane Via an acyclic amino group such as -NHR. Such H-bonded systems may also have some bearing on our understanding of the mechanism of action of cyclo-AMP, which possesses a saturated 1,3,2-dioxaphosphorinane ring.9 One account of a comparison of the structures of tri- and pentacoordinated systems given by Holmes et al. relates to the compounds IV and V, which contain different acyclic groups.4 (8) The other case wherein a chair conformation is found for the dioxaphosphorinane ring occupying an a-e position in a TBP arrangement is (2,6-Me2C6H3S)(C6F5O)2P(OCH2CMe2CH2O). Such an observation has been ascribed to a combination of an electronegativity effect and a steric effect: Hans, J.; Day, R. O.; Howe, L.; Holmes, R. R. Inorg. Chem. 1991, 30, 3132. (9) Holmes, R. R.; Deiters, J. A. Inorg. Chem. 1994, 33, 3235 and references cited therein.

© 1997 American Chemical Society

Cyclic Aminophosphites and -phosphoranes

Inorganic Chemistry, Vol. 36, No. 10, 1997 2045

However, no conformational change was observed for the 1,3,2dioxaphosphepin ring in this pair.

For structural studies as well as for a comparative assessment of the relative reactivity, a pair of substrates such as VI and VII is very useful because the acyclic amino substituent can lend itself as a replaceable group. Use of aminophosphines as

precursors for cyclic phosphites is fairly common;10 however, a knowledge of the relative ease of amino substitution in VI and VII is not available. This information could be useful for preparing phosphoranes with the desired substituents. Compounds of the type VII will also be helpful in assessing the ring size effects on 31P NMR chemical shifts.11 When R1 ) H, the effects of H-bonding on the structures may be investigated. In this article, we report the X-ray structures of the pairs 1, 2 and 3, 4‚1/2Et2O); the acyclic cyclo-C6H11NH group was chosen to introduce H-bonding. Synthesis and spectra of the

spirocyclic phosphoranes 5-9 and identification of related aminophosphoranes is also described; the relative reactivities of selected phosphoranes and their tricoordinated counterparts are compared. Experimental Section Chemicals were procured from Aldrich/Fluka or from the local manufacturers; they were purified when required. Solvents were purified according to standard procedures.12 All reactions, unless stated (10) (a) Nifant’ev, E. E.; Koroteev, M. P.; Pugashova, N. M.; Kukhareva, T. S.; Borisenko, A. A. Zh. Obshch. Khim. 1981, 51, 1900 [Engl. ed. p 1632 (1982)]. (b) Nelson, K. A.; Bentrude, W. G.; Setzer, W. N.; Hutchinson, J. P. J. Am. Chem. Soc. 1987, 109, 4058. (11) (a) Holmes, R. R.; Prakasha, T. K.; Pastor, S. D. In Phosphorus-31 NMRsSpectral Properties in Compound Characterization and Structural Analysis; Quin, L. D., Verkade, J. G., Eds.; VCH: New York, 1994; Chapter 3. (b) Holmes, R. R.; Prakasha, T. K. Phosphorus, Sulfur, Silicon 1993, 80, 1 and references cited therein. (12) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; Pergamon: Oxford, UK, 1986.

otherwise, were performed under dry nitrogen atmosphere. 1H, 13C, and 31P{1H} NMR spectra were recorded on Bruker 200 MHz spectrometer in CDCl3 solutions (unless stated otherwise), with shifts referenced to SiMe4 (δ ) 0) or 85% H3PO4 (δ ) 0). IR spectra were recorded on a JASCO FT/IR-5300 spectrophotometer. Elemental analyses were carried out on a Perkin-Elmer 240C CHN analyzer. The cyclic compounds (C6H11NH)P(OCH2CMe2CH2O) (1), (C6H11NH)P{(O-(t-Bu)2C6H2)2CH2} (3), (C6H11NH)P(1,2-O2C6H4) (10), (C6H11NH)P(2,2′-OC6H4-C6H4O) (11), and (2,6-Me2C6H3O) P(OCH2CMe2CH2O)(1,2-O2C6Cl4) (X) were prepared as described before.13 The compound (C6H11NH)P{(O-(2-t-Bu)(4-Me)C6H2)2CH2} (12) was also prepared similarly. More physical data for 1 and 3 are described below; data for other compounds are given as Supporting Information. 1 (sublimed product used as such for X-ray crystallography): mp 78 °C (bp 136 °C/0.5 mmHg); 1H NMR (CDCl3) δ 0.92 (s, 3H, CH3), 1.02 (s, 3H, CH3), 1.00-2.10 (m, 10H, cyclohexyl-H), 2.95 (br, 1H, NH), 3.20 (br, 1H, N-CH), 3.60-3.85 (m, 4H, OCH2); 13C NMR δ 21.94, 22.81 (two s, CH3), 25.4, 25.6 (s each, CCH2), 32.75 (d, 3J ) 6.5 Hz, CMe ), 37.30 (d, J ) 3.5 Hz, NCCH ), 49.65 (d, 2J ) 2 2 15.5 Hz, NCH), 72.07 (s, OCH2); 31P NMR δ 132.1. Anal. Calcd for C11H22NO2P: C, 57.14; H, 9.52; N, 6.06. Found: C, 57.01; H, 9.50; N, 6.51. The unsublimed but recrystallized (from n-hexane) product showed essentially the same 1H and 31P NMR spectra [δP of 118.8 ppm reported earlier13 is incorrect]. Even in toluene-d8, we could not effect clearcut separation of the peaks for calculating the coupling constants. 3 (recrystallized from hexane for X-ray work): mp 212 °C; 1H NMR δ 1.32 (s, 18H, t-Bu-H), 1.45 (s, 18H, t-Bu-H), 1.10-2.25 (m, 10H, cyclohexyl-H), 2.90 (dd, 2J ≈ 25 Hz, 3J ≈ 11 Hz, 1H, NH), 3.42 (d, 2 J ≈ 14 Hz, 1H, CHAHB), 3.75 (br, 1H, N-CH), 4.42 (dd, 2J ≈ 14 Hz, J(P-H) ≈ 3 Hz), 7.20-7.40 (m, 4H, Ar-H); 31P NMR δ 140.9. Anal. Calcd for C35H54NO2P: C, 76.22; H, 9.80; N, 2.54. Found: C, 76.10: H, 9.65; N, 2.54. The phosphoranes 2 and 4-9 were prepared by oxidative addition reactions of quinones (procedure a) or diols (procedure b) to the phosphites; only typical procedures are given. (i) Preparation of (C6H11NH)P(OCH2CMe2CH2O)(1,2-O2C6Cl4) (2) (Procedure a). Tetrachloro-o-benzoquinone (0.3 g, 1.58 mmol) was added to 1 (0.36 g, 1.58 mmol) in dry toluene (5 mL). The mixture was stirred for 10 min, solvent removed in Vacuo, and the residue crystallized from dichloromethane-hexane mixture (1:2). Yield: 0.45 g (60%); mp 127 °C; 1H NMR δ 0.90-2.10 (m, 10H, cyclohexyl-H), 1.00 (s, 3H, CH3), 1.05 (s, 3H, CH3) 3.03 (br dd, 1H, NH), 3.32 (br, 1H, NCH), 3.94 (d, J ≈ 20 Hz, 4H, OCH2); 31P NMR δ -45.7. Anal. Calcd for C17H22Cl4NO4P: C, 42.78; H, 4.61; N, 2.94. Found: C, 42.61; H, 4.60; N, 3.00. (ii) Preparation of (C6H11NH)P{(O-t-Bu)2C6H2)2CH2}(1,2-O2C6H4)‚ 1/ Et O (4‚1/ Et O) (Procedure b). To a mixture of 10 (1.25 g, 5.28 2 2 2 2 mmol) and CH2[(t-Bu)2C6H2OH]2 (2.24 g, 5.28 mmol) in dry ether (40 mL) maintained at -60 °C was added N-chlorodiisopropylamine (0.72 (13) Said, M. A.; Kumara Swamy, K. C.; Veith, M.; Huch, V. J. Chem. Soc., Perkin Trans. 1 1995, 2945.

2046 Inorganic Chemistry, Vol. 36, No. 10, 1997 g, 5.28 mmol) in ether (30 mL) over a period of 15 min with continuous stirring. The mixture was brought to 30 °C, stirred overnight, and filtered. The product was crystallized from a mixture of dichloromethane-hexane (1:2). Yield: 2.5 g (72%); mp 173-5 °C; IR (cm-1) 3440 (ν (N-H)); 1H NMR δ 1.03-2.03 (m, 46H, cyclohexyl-H + t-Bu-H), 3.32-3.52 (br, 2H, NH + NCH), 4.07 (br d, 1H, CHAHB), 4.60 (br d, 1H, CHAHB), 6.72-7.35 (m, 8 H, Ar-H); 31P NMR δ -56.3, -56.8 (these values were too close to ascertain the exact shift for the crystal chosen for X-ray). Anal. Calcd for C41H58NO4P (after evacuating at 0.3 mmHg for 3 h): C, 74.60; H, 8.80; N, 2.12. Found: C, 73.93; H, 9.05; N, 2.10. (iii) Preparation of (C6H11NH)P(1,2-O2C6H4)(1,2-O2C6Cl4) (5) (Procedure a). Quantities used: phosphite 10, 0.90 g, 3.79 mmol; tetrachloro-1,2-benzoquinone, 0.93 g, 3.79 mmol. Yield: 1.1 g (60%, after recrystallization from dichloromethane-hexane (1:2)); mp 182 °C; IR (cm-1) 3368 (sharp); 1H NMR δ 1.05-1.95 (m, 10H, cyclohexylH), 3.10-3.35 (m, 2H, NH and NCH), 6.80-7.30 (m, 4H, Ar-H); 31P NMR δ -29.4. Anal. Calcd for C18H16Cl4NO4P: C, 44.74; H, 3.31; N, 2.90. Found: C, 44.53; H, 3.29; N, 3.76. (iv) Preparation of (C6H11NH)P(OCH2CMe2CH2O)(9,10-O2C14H8) (6) (Procedure a). Quantities used: phosphite 1, 0.76 g, 3.31 mmol; 9,10-phenanthrenequinone, 0.69 g, 331 mmol. Yield: 0.9 g (62%); mp 158 °C; IR (cm-1) 3350 (sharp); 1H NMR δ 1.03, 1.08 (two s, 6H, 2CH3), 1.00-2.20 (m, 10H, cyclohexyl-H), 3.12 (dd, 1H, NH), 3.21 (m, 1H, NCH), 3.90-4.20 (m (AB), 4H, OCH2), 7.40-8.65 (m, 8H, Ar-H); 31P NMR δ -46.2. Anal. Calcd for C25H30NO4P: C, 68.34; H, 6.83; N, 3.20. Found: C, 68.21; H, 6.75; N, 3.50. (v) Preparation of (C6H11NH)P(2,2′-OC6H4-C6H4O)(9,10-O2C14H8) (7) (Procedure a). Quantities used: phosphite 11, 03.2 g, 10.51 mmol; 9,10-phenanthrenequinone, 2.19 g, 10.51 mmol. Yield (after recrystallization from dichloromethane-hexane (1:2)): 3.5 g (64%); mp 185 °C; IR (cm-1) 3381, 3450 (ν (N-H)); 1H NMR δ 0.90-2.20 (m, 10H, cyclohexyl-H), 3.25-3.60 (m, 2H, NH and NCH), 7.22-8.72 (m, 16H, Ar-H); 31P NMR δ -34.4. Anal. Calcd for C32H28NO4P: C, 73.70; H, 5.37; N, 2.69. Found: C, 73.17; H, 5.46; N, 3.13. (vi) Preparation of (C6H11NH)P{(O-(2-t-Bu)(4-Me)C6H2)2CH2}((O2C6Cl4) (8) (Procedure a). Quantities used: phosphite 12, 1.34 g, 2.88 mmol; tetrachloro-o-benzoquinone, 0.71 g, 2.88 mmol; and benzene, 5 mL [Warning: Benzene is a carcinogen; all operations involving this solvent should be performed inside an efficient hood.] Yield (after crystallization from dichloromethane-hexane mixture (1: 2)): 1.1 g (54%); mp 118 °C; IR (cm-1) 3366 (sharp, ν (N-H)); 1H NMR δ 0.72-2.52 (m, 34H, cyclohexyl-H + CH3), 3.25-3.70 (m, 3H, CHAHB + NH + NCH), 4.55 (d, 1H, 2J ) 14 Hz, CHAHB), 6.75-7.15 (m, 4H, Ar-H); 31P NMR δ -54.6. Anal. Calcd for C35H42Cl4NO4P: C, 58.92; H, 5.89; N, 1.96. Found: C, 59.05; H, 6.10; N, 1.76. (vii) Preparation of (C6H11NH)P(2,2′-OC6H4C6H4O)2 (9) (Procedure b). Quantities used: phosphite 11, 1.25 g, 3.99 mmol; 2,2′biphenol, 0.74 g, 3.99 mmol; and N-chlorodiisopropylamine, 0.54 g, 3.99 mmol. Yield (after crystallization from dichloromethane-hexane (1:2)): 1.5 g (79%); mp 209-212 °C; 1H NMR δ 0.80-2.10 (br m, 10H, cyclohexyl-H), 3.35 (br, 2H, NH + NCH), 6.90-7.65 (m, 16H, Ar-H); 31P NMR δ -39.6. Anal. Calcd for C30H28NO4P: C, 72.43; H, 5.63; N, 2.82. Found: C, 72.42; H, 6.03; N, 2.57. (viii) Preparation of (C6H11NH)P(O)(OCH2CMe2CH2O) (13). This compound was prepared by reacting (OCH2CMe2CH2O)P(O)Cl14 with 2 mol equiv of cyclohexylamine in diethyl ether: mp 172 °C; 1H NMR δ 0.88 (s, 3H, CH3), 1.20 (s, 3H, CH3), 0.88-2.12 (m, 10H, cyclohexyl-H), 2.72 (m, 1H, NH), 3.10 (br, 1H, NCH), 3.80 (dd, 2H, OCH2(A)), 4.30 (dd, 2H, OCH2(B)); 31P NMR δ 4.4. Anal. Calcd for C11H22NO3P: C, 53.44; H, 8.91, N, 5.67. Found: C, 53.82; H, 9.32; N, 6.48. (ix) Reaction of 1 with Ethylene Glycol/N-Chlorodiisopropylamine (Procedure b). Quantities used: phosphite 1, 1.55 g, 6.71 mmol; ethylene glycol, 0.42 g, 6.71 mmol; and N-chlorodiisopropylamine, 0.91 g, 6.71 mmol. The compounds 13 (0.3 g, 20%) and [(OCH2CH2O)2P]2(OCH2CMe2CH2O) (14, 0.2 g, 14%) were isolated by fractional crystallization from the reaction mixture. Compound 14 (very hygroscopic): mp 145 °C; 1H NMR δ 0.93 (s, 6H, CH3), 3.65(14) Zwierzak, A. Can. J. Chem. 1954, 37, 1498.

Said et al. 3.95 (m, 20H, OCH2); 31P NMR δ -28.1. Anal. Calcd for C13H26O10P2: C, 38.61; H, 6.44. Found: C, 40.18; H, 7.11. Reactivity of Cyclic Phosphites and Phosphoranes. (i) Hydrolysis. Compound 2 (0.085 g) was dissolved in THF (5 mL) and kept in open air until all the solvent evaporated (ca. 24 h). Analysis of the product mixture by 31P and 1H NMR, after completely evaporating the solvent in Vacuo, showed that it contained 13 (δP 4.2; 40%) and other unidentified products [δP -2.5 ca. 45%), -8.6 (ca. 10%), -7.5 (ca. 3%)]; the compound (OCH2CMe2CH2O)P(HOC6Cl4O) (15) was not detected. Under identical conditions using similar molar quantities, 1 hydrolyzed to HOCH2CMe2CH2OP(O)(H)(O)-(H3NC6H11)+ (IX) quantitatively, whereas 6 and 7 were recovered unchanged. The compound X13 gave 15 (50%): mp 215 °C; 1H NMR δ 0.99 (s, 3H, CH3), 1.38 (s, 3H, CH3), 4.08 (dd, J ) 11.0, 23.6 Hz, 2H, OCH2(A)), 4.60 (d, J ) 11.0 Hz, OCH2 (B)); 31P NMR δ -11.4. Anal. Calcd for C11H11Cl4O5P: C, 33.33; H, 2.77. Found: C, 33.64; H, 2.90. The same compound 15 was obtained as a major isolable product (50%) when (PhO)P(OCH2CMe2CH2O) was reacted with o-chloranil. (ii) Reaction with 8-Hydroxyquinoline. A mixture of 1 (0.19 g, 0.83 mmol) and 8-hydroxyquinoline (0.12 g, 0.83 mmol) in toluene (10 mL) was heated under reflux for 5 h. The compound (NC9H6O)P(OCH2CMe2CH2O) (XI) [δP 113.8;15 isolated] was obtained quantitatively. Under identical conditions, 6 and 13 did not react. Compound 11 reacted with 8-hydroxyquinoline (1.67 mmol each) in refluxing p-xylene (20 mL, 10 h) to give (NC9H6O)P(2,2′-OC6H4C6H4O) (XII) (15%, δP 140.1), 11 (80%), and another product (5%) with δP of 11.6 ppm. The pentacoordinated derivatives 7 and 17 did not react under identical conditions. X-ray Crystallography Experimental Section. Crystal data for 1-3 and 4‚1/2Et2O are summarized in Table 1. Data for 1, 2, and 4‚1/2Et2O were collected at -120 °C on a Stoe-Siemens-Huber diffractometer and for 3 at -80 °C on a Stoe-Siemens-AED diffractometer with monochromated Mo KR radiation (λ ) 0.710 73 Å). The structures were solved by direct methods.16 All non-hydrogen atoms were refined anisotropically.17 For the hydrogen atoms bonded to carbon atoms, the riding model was used. The hydrogens bonded to nitrogen were refined with distance restraints. The structures were refined against F2 with a weighting scheme of w-1 ) σ2(Fo2) + (g1P)2 + g2P, with P ) (Fo2 + 2Fc2)/3. The R values are defined as R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) [∑w(Fo2 - Fc2)2/∑wFo4]0.5. In structures 3 and 4‚1/2Et2O, one tert-butyl group is disordered. The anisotropic displacement parameters of the carbon atoms opposite to each other are fixed to the same values. Also, distance restraints were used. Additionally, in structure 4‚1/2Et2O, the ether molecule is severely disordered. It is refined with distance restraints and restraints for the displacement parameters. In structure 1, there are four independent molecules in the asymmetric unit. Each two of them are related by a pseudoinversion center at -0.118, 0, -0.106. A transformation to a centrosymmetric space group was not possible.

Results and Discussion Synthesis, Reactivity, and Spectra. The pentacoordinated compounds 2 and 4-9 are readily synthesized by oxidative addition reaction of the cyclic phosphite with a quinone (2, 5-8) or a diol (4, 9). The reaction using diol is illustrated for the synthesis of 4 (eq 1). However, when (C6H11NH)P(OCH2CMe2CH2O) (1) was reacted with ethylene glycol/ClN(i-Pr)2, we could not isolate the expected phosphorane, (C6H11NH)P(OCH2CMe2CH2O)(OCH2CH2O) (VIII); instead, the phosphoramidate 13 and a diphosphorane formulated as [(OCH2CH2O)2]2P(OCH2CH2O) (14) were isolated as crystalline solids (eq 2). It can be noted that δP for 14 is close to that of the monophosphorane (15) Said, M. A.; Pu¨lm, M.; Irmer, R. H.; Kumara Swamy, K. C. J. Am. Chem. Soc. 1996, 118, 9841. (16) Sheldrick, G. M. SHELXS-90. Acta Crystallogr. 1990, A46, 467. (17) Sheldrick, G. M. SHELXS-93, University of Go¨ttingen, 1993.

Cyclic Aminophosphites and -phosphoranes

Inorganic Chemistry, Vol. 36, No. 10, 1997 2047

Table 1. Crystal Data for 1-4 empirical formula formula weight crystal system space group a/Å b/Å c/Å R/deg β/deg γ/deg V/Å3 Z Dcalc/g cm-3 λ/Å T/°C µ/cm-1 F(000) cryst size/(mm3) 2θ range reflect coll indep reflect Rint data parameters restraints S R1 [I > 2σ(I)]a wR2 )all data)a Flack x18 largest diff peak/eÅ-3 largest diff hole/eÅ-3 a

1

2

3

4‚1/2Et2O

C11H22NO2P 231.27 orthorhombic Pna21 18.287(2) 15.157(1) 18.541(3) 90 90 90 5139(1) 16 1.196 0.710 73 -120 1.98 2016 0.5 × 0.4 × 0.2 7-45 8219 6689 0.0395 6658 561 7 1.021 0.0584 0.1210 0.0(1) 0.241

C17H22Cl4NO4P 477.13 monoclinic P21/c 9.845(1) 17.923(4) 12.344(2) 90 107.47(1) 90 2077.7(6) 4 1.525 0.710 73 -120 6.70 984 0.6 × 0.4 × 0.4 4-50 4945 3681 0.0205 3672 249 1 1.052 0.0382 0.1107

C35H54NO2P 551.76 triclinic P1h 9.676(3) 13.060(3) 13.969(4) 96.97(2) 103.96(2) 96.53(2) 1681.6(8) 2 1.090 0.710 73 -80 1.11 604 0.6 × 0.4 × 0.4 5-45 4941 4406 0.0669 4403 375 31 1.027 0.0585 0.1639

C41H58NO4P‚0.5(CH3CH2)2O 696.91 monoclinic P21/n 9.499(1) 18.971(1) 23.478(2) 90 95.93(1) 90 4208.2(6) 4 1.100 0.710 73 -120 1.05 1516 0.6 × 0.5 × 0.4 7-50 9259 7458 0.0599 7453 537 240 1.028 0.0634 0.1864

0.440

0.398

0.669

-0.355

-0.297

-0.406

-0.210

R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) [∑w(Fo 2

Fc2)2/∑wFo4]0.5.

upon treating 1 with THF/water; even exposing a THF solution of 1 to air for 24 h leads to IX quantitatively (eq 3). The pentacoordinated 2 hydrolyzed to give 13 as one of the major products (eq 4); the identity of 13 is confirmed by an (3)

(1)

(EtO)P[OCH2CH2O]2 (δP -27.0 ppm19). Compound 14 is very sensitive to moisture.

(4)

independent synthesis. This reaction is interesting because, when the (2,6-dimethylphenoxy)phosphorane X13 is hydrolyzed, the crystalline product obtained, 15, has the five-membered ring residue connected to phosphorus (eq 5); this latter product is not detected in the hydrolysis of 2 (31P NMR). The rationale

(2)

(5)

Hydrolytically, 1 is much less stable than 2, 6, or 13. As reported by us before,13 the ring-opened product IX is obtained

for the difference in the hydrolysis of 2 and X may lie in the relative apicophilicities of the NHC6H11 and OPh groups in a trigonal bipyramidal environment. As can be expected,10 the cyclohexylamino group in 1 can be readily replaced by an aryloxy group (eq 6). By contrast,

(18) Flack, H. D. Acta Crystallogr. 1983, A39, 876. (19) Chang, B. C.; Conrad, W. E.; Denney, D. B.; Denney, D. Z.; Edelman, R.; Powell, R. L.; White, D. W. J. Am. Chem. Soc. 1971, 93, 4004.

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Said et al.

both 13 and the aminophosphorane 2 do not undergo replacement of the NHC6H11 group under similar experimental conditions. The replacement of the amino group in 11 is not as facile

(6)

as it is in 1, and the product XII is formed in 15% yield after refluxing 11 with 8-hydroxyquinoline for 10 h in p-xylene. The

Table 2. 31P NMR Data for Aminophosphoranes Along with Ring System Assignment compound compound ring ring no.a no.a system δP (ppm) system 5 16 2 6 7 17

5+5 5+5 5+6 5+6 5+7 5+7

-29.4 -28.2 -45.5 -46.2 -34.4 -36.6

4 8 18 19 9 20

5+8 5+8 6+7 6+8 7+7 7+8

δP (ppm) -56.3, -56.8 -54.6 -54.2 -70.3 -39.6 -58.8

a Compound 17 is pure by 31P NMR but could not be crystallized; 16 and 18-20 have been identified by NMR but not isolated in a pure state

corresponding pentacoordinated derivative 7 does not react; both the eight-membered ring compounds 3 and 4 are also unreactive, probably due to steric factors. The difference in reactivity between the tri- and pentacoordinated amino compounds cannot be simply due to steric factors, because the pentacoordinated phenoxy derivative XIII20 is readily hydrolyzed21 in THF solution to the ring-opened product XIV, whereas the corresponding amino compound 6 is resistant

Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for 1 P(1)-O(2) P(1)-N(1) P(2)-O(4) P(3)-O(5) P(3)-N(3) P(4)-O(7)

to hydrolysis under these conditions; thus, there does not appear to be severe hindrance for nucleophilic attack. At this point, we can only say that both lability and strength of the P-N bond may contribute to the difference. In fact, it can be noted that the P-N bond is longer in the phosphites 1 and 3, albeit marginally, than in the phosphoranes 2 and 4, respectively (see X-ray section). The OCH2 region in the 1H NMR spectrum (24 °C) of 6 is similar to that observed for XV; 2 shows a broad doublet

O(2)-P(1)-O(1) O(1)-P(1)-N(1) O(3)-P(2)-N(2) O(5)-P(3)-O(6) O(6)-P(3)-N(3) O(8)-P(4)-N(4)

1.624(5) 1.652(5) 1.638(5) 1.629(5) 1.646(5) 1.638(4) 98.6(2) 101.3(2) 100.7(2) 98.9(2) 100.4(2) 107.3(3)

P(1)-O(1) P(2)-O(3) P(2)-N(2) P(3)-O(6) P(4)-O(8) P(4)-N(4) O(2)-P(1)-N(1) O(3)-P(2)-O(4) O(4)-P(2)-N(2) O(5)-P(3)-N(3) O(8)-P(4)-O(7) O(7)-P(4)-N(4)

1.642(4) 1.637(4) 1.657(5) 1.636(4) 1.632(5) 1.671(5) 107.7(3) 99.3(3) 106.9(3) 108.1(3) 99.7(2) 100.6(3)

Figure 1. ORTEP plot of 1. Only phosphorus, nitrogen, oxygen, and the carbon connected to nitrogen are labeled.

[3J(P-H) ) 20 Hz] for the OCH2 protons, which is analogous to the high-temperature (g41 °C) spectrum of XV. We ascribe these features to the a-e S e-a processes in a TBP structure as described by Holmes et al.,2a with the difference that a diequatorial disposition of the six-membered ring as shown in (20) Sarma, R.; Ramirez, F.; Mckeever, B.; Marecek, J. F.; Lee, S. J. Am. Chem. Soc. 1976, 98, 581. (21) In fact, the hydrolyzed compound was obtained earlier in an attempt to prepare the pentaoxyphosphorane20 by the oxidative addition of the quinone to the phosphite, see: Gallucci, J. C.; Holmes, R. R. Inorg. Chem. 1980, 19, 3540.

2′ could contribute to the equivalence of protons in 2.

The 31P NMR data for the aminophosphoranes listed according to ring size are shown in Table 2. As observed for tetra-22 and hexacoordinated phosphoranes,15 fiVe- and seVen-membered

Cyclic Aminophosphites and -phosphoranes

Inorganic Chemistry, Vol. 36, No. 10, 1997 2049

Figure 2. ORTEP plot of 1 showing the H-bonding interactions.

Figure 4. ORTEP plot of 3. Only the phosphorus, nitrogen, and atoms of the eight-membered ring are labeled. Also shown at the bottom is the conformation of the 1,3,2-dioxaphosphocin ring. Figure 3. ORTEP plot of 2. Only the phosphorus atom and those connected to it are labeled. Also shown is the conformation of the 1,3,2dioxaphosphorinane ring with all the ring atoms labeled.

rings tend to deshield the phosphorus relative to six- and eightmembered rings. This effect has also been observed for pentaoxyphosphoranes XVI-XX reported by Holmes et al.3a,11 These data are suggestive of a ring size effect, with five- as well as seven-membered rings deshielding the phosphorus in 31P NMR. Figure 5. ORTEP plot of 3 showing H-bonding interactions.

Structural Aspects. Compound 1 crystallizes in space group Pna21 with four independent but similar molecules in the asymmetric unit. In Figure 1, the structure and atomic labeling of one of the molecules is shown, while selected bond lengths and angles of all four molecules are listed in Table 3. All (22) Said, M. A.; Kumara Swamy, K. C.; Chandra Mohan, K.; Venkata Lakshmi, N. Tetrahedron 1994, 50, 6989.

Figure 6. ORTEP plot of 4. Atoms of the 1,3,2-dioxaphosphocin ring and those connected to phosphorus are labeled. Also shown at the bottom is the conformation of the 1,3,2-dioxaphosphocin ring.

molecules are connected by hydrogen bonds [H(1)-O(7A) ) 2.22(3), H(2)-O(6) ) 2.18(3), H(3)-O(1) ) 2.23(3), and H(4)-O(3) ) 2.18(3) Å], leading to chains (Figure 2). In the pentacoordinated compound 2 (Figure 3), by contrast, hydrogen

2050 Inorganic Chemistry, Vol. 36, No. 10, 1997

Said et al.

Table 4. Selected Bond Lengths (Å) and Bond Angles (deg) for 2 P(1)-O(1) P(1)-O(2) P(1)-O(4)

1.5929(19) P(1)-N(1) 1.6225(18) P(1)-O(3) 1.7837(18)

O(1)-P(1)-N(1) 123.81(11) N(1)-P(1)-O(2) 92.01(11) N(1)-P(1)-O(3) 122.90(11) O(1)-P(1)-O(4) 85.34(9) O(2)-P(1)-O(4) 177.58(10)

1.619(2) 1.6574(19)

O(1)-P(1)-O(2) 97.05(10) O(1)-P(1)-O(3) 112.45(10) O(2)-P(1)-O(3) 90.09(9) N(1)-P(1)-O(4) 86.95(10) O(3)-P(1)-O(4) 88.65(9)

Table 5. Selected Bond Lengths (Å) and Bond Angles (deg) for 3 P(1)-N(1) P(1)-O(2) N(1)-P(1)-O(1) O(1)-P(1)-O(2)

1.635(3) 1.670(2) 94.89(13) 101.56(11)

P(1)-O(1) N(1)-P(1)-O(2)

1.662(2) 100.39(14)

Table 6. Selected Bond Lengths (Å) and Bond Angles (deg) for 4 P(1)-O(1) P(1)-O(3) P(1)-O(4) O(1)-P(1)-N(1) N(1)-P(1)-O(3) N(1)-P(1)-O(2) O(1)-P(1)-O(4) O(3)-P(1)-O(4)

1.606(2) 1.636(2) 1.716(2) 118.08(12) 125.18(12) 89.02(11) 85.80(10) 90.06(10)

P(1)-N(1) P(1)-O(2) O(1)-P(1)-O(3) O(1)-P(1)-O(2) O(3)-P(1)-O(2) N(1)-P(1)-O(4) O(2)-P(1)-O(4)

1.629(2) 1.669(2) 116.60(11) 95.67(10) 89.40(10) 90.17(11) 178.53(11)

bonds are absent. The phosphite 3 forms dimers by weak hydrogen bonds (H(1N)-O(1A) ) 2.56(2) Å) (Figures 4 and 5), while there are, again, no hydrogen bonds in the corresponding pentacoordinated structure of 4‚1/2Et2O (Figure 6). Selected bond lengths and angles for 2-4 are given in Tables 4-6. In the tricoordinated structures 1 and 3, the phosphorus atom has trigonal pyramidal geometry, while in the pentacoordinated compounds 2 and 4 it is trigonal bipyramidal (TBP) with the rings apical-equatorial and the acyclic cyclohexylamino group equatorial. By contrast, in XXI23 and XXII,15 which have the same phosphocin ring as in 4, the phenyl or the oxinate group is apical. Although oxinate may be expected to be more

apicophilic because of higher electronegativity, the phenyl and the cyclohexylamino groups should have comparable group electronegativities (-Ph, 2.58; -NMe2, 2.61; -NHC6H11, data not available) on the Pauling scale.24 Thus, the preference of -NHC6H11 to be equatorial may be due to the π-interaction involving the lone pair on nitrogen and an unused d orbital on phosphorus in 4. The sum of the bond angles around N(1) in 4 shows that it is nearly planar and, hence, is possibly involved in π-interaction with phosphorus. The 1,3,2-dioxaphosphorinane ring in 1 adopts a chair conformation, which is quite typical for tricoordinated cyclic phosphites.6,7,25 However, in contrast to Verkade’s compounds XXIII,7 the nitrogen in 1 is disposed toward the axial position; (23) Timosheva, N. Y.; Prakasha, T. K.; Chandrasekaran, A.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1995, 34, 4525. (24) Huheey, J. E. Inorganic Chemistry, 3rd ed.; Harper International: Cambridge, UK, 1983; p 156. (25) Huang, Y.; Mullah, N. N.; Sopchik, A. E.; Arif, A. M.; Bentrude, W. G. Tetrahedron Lett. 1991, 32, 899.

this feature may be due to the presence of H-bonding in 1. In the corresponding pentacoordinated phosphorane 2, the same phosphorinane ring adopts a boat conformation, with P(1), O(1), C(13), and C(12) forming the base of the boat (mean deviation, 0.010(1) Å). Atoms O(2) and C(11) are displaced from this plane by 0.592(3) and 0.642(4) Å, respectively. As explained by Trippett26 and later by Holmes et al.,27 this is the most favored conformation for this ring located apical-equatorially in a TBP structure. The dihedral angle between the equatorial plane and the endocyclic P-Oeq-C bond is 80.7(2)°; this is not too far from 90° and is in the typical range for this kind of structure.2a Such a feature allows the lone pair of the equatorial oxygen to approach the equatorial plane, favoring the boat conformation for the phosphorinane ring.26 The five-membered rings in 2 and 4 are planar (mean deviation, 0.007(2) Å in 2 and 0.018(2) Å in 4). Here, the dihedral angles between the equatorial plane and the endocyclic P-Oeq-C bond are 87.4(2)° and 83.7(2)°, respectively. The eight-membered ring adopts a boat-chair conformation28a in 3 (Figure 4). This seems to be the typical conformation in cyclic phosphites28 and in pentacoordinated phosphoranes when the ring spans a diequatorial position (e.g., XXI and XXIII).3c,g,15 This ring exhibits a distorted tub conformation when it is located apical-equatorially3a,d as in structure 4 (Figure 6). Atoms O(2), C(21), C(11), and C(16) are coplanar to within 0.001(1) Å, while atoms P(1), O(1), C(22), and C(1) depart at the same side from this plane by 1.223(3), 0.977(4), 0.417(5), and 0.978(4) Å, respectively. The dihedral angle between the equatorial plane and the plane containing the endocyclic P-Oeq-C bond is 85.2(2)°. The P-N bond lengths are shortened in the P(V) compounds compared to the P(III) structures [P-N (mean) ) 1.657 Å in 1, P(1)-N(1) ) 1.619(2) in 2, 1.635(3) in 3, and 1.629(2) Å in 4]. All of these are shorter than the value of 1.73 Å calculated for a P-N single bond by the modified Schomaker-Stevenson equation.29 The P-O bonds differ depending on the ring size.2a,3b As expected, the apical bond lengths in the TBP structures are longer than the corresponding equatorial values, and both are shorter than the equivalent bonds in the tricoordinated structures. Because of ring strain, the P-O bonds in the unsaturated fivemembered rings are the longest [P-Oeq ) 1.657(2) Å, P-Oap ) 1.784(2) Å in 2; P-Oeq ) 1.636(2) Å, P-Oap ) 1.716(2) Å in 4]. The P(1)-O(4) bond in 2 is even 0.11 Å longer than the value of 1.67 Å which is calculated for a P-O single bond by Blom and Haaland.29 As observed before,2a the bond lengths in the six-membered rings are the shortest [P(1)-Oeq ) 1.593(26) Trippett, S. Pure Appl. Chem. 1974, 40, 595. (27) Holmes, R. R.; Day, R. O.; Deiters, J. A.; Kumara Swamy, K. C.; Holmes, J. M.; Hans, J.; Burton, S. D.; Prakasha, T. K. In Phosphorus ChemistrysDeVelopments in American Science; (Walsh, E. N., Parry, R. W., Quin, L. D., Eds.; American Chemical Society: Washington, DC, 1992; Chapter 2. (28) (a) Arshinova, R. P. Russ. Chem. ReV. 1988, 57, 1142. (b) Litvinov, I. A.; Struchkov, Yu. T.; Arbuzov, B. A.; Arshinova, R. P.; Ovodova, O. V. Zh. Strukt. Khim. 1984, 25, 118. (c) Kataeva, O. N.; Litvinov, I. A.; Naumov, V. A.; Mukmeneva, N. A. Zh. Strukt. Khim. 1989, 30, 166. (d) Elnagar, H. Y.; Layman, W. J.; Fronczek, F. R. Acta Crystallogr. 1995, C51, 1177. (e) Pastor, S. D.; Shum, S. P.; Debellis, A. D.; Burke, L. P.; Rodenbaugh, R. K.; Clarke, F. H.; Rihs, G. Inorg. Chem. 1996, 35, 949. (29) Blom, R.; Haaland, A. J. Mol. Struct. 1985, 128, 21.

Cyclic Aminophosphites and -phosphoranes (2) Å, P(1)-Oap ) 1.623(2) Å in 2; P-O (mean) ) 1.635 Å in 1], while the bonds in the eight-membered rings are in a middle range [P(1)-O(2) ) 1.670(2) Å, P(1)-O(1) ) 1.662(2) Å in 3; P-Oeq ) 1.606 Å, P-Oap ) 1.669 Å in 4]. The angles at phosphorus in the tricoordinated structures vary from 98.6(2)° (O(2)-P(1)-O(1)) to 108.1(3)° (O(5)-P(3)N(3)) in 1 and from 94.9(1)° (N(1)-P(1)-O(1)) to 101.6(1)° (O(1)-P(1)-O(2)) in 3. The equatorial angles in the trigonal bipyramids are in the range from 112.5(1)° (O(1)-P(1)-O(3)) to 123.8(1)° (O(1)-P(1)-N(1)) in 2 and in the range from 116.6(1)° (O(1)-P(1)-O(3)) to 125.2(1)° (N(1)-P(1)-O(3)) in 4, while the angles involving the apical atoms are 177.6(1)° in 2 and 178.5(1)° in 4. By using the dihedral angle method,30 the geometry is found to be displaced along the pseudorotational coordinate to an extent of 11.0% for 2 and 10.9% for 4 from the ideal trigonal bipyramid toward the square pyramid, with O(1) as the pivotal atom. Summary The hydrolysis of pentaoxyphosphoranes and aminophosphoranes leads to different sets of products. Replacement of the amino group in a phosphite is much more facile than that in the aminophosphoranes studied in this work. The -NH proton of the -HNC6H11 group participates in H-bonding in the phosphites but not in the corresponding pentacoordinated phosphoranes. The amino group in phosphite 1 (which contains the phosphorinane ring) occupies the axial position, possibly because of H-bonding. The change in conformation for a 1,3,2dioxaphosphorinane ring from chair in cyclic phosphites to boat (30) (a) Holmes, R. R.; Deiters, J. A. J. Am. Chem. Soc. 1977, 99, 3318. (b) Spek, A. L. Acta Crystallogr. 1990, A46, C34.

Inorganic Chemistry, Vol. 36, No. 10, 1997 2051 when this ring is located apical-equatorially in a trigonal bipyramidal arrangement is firmly established by our choice of the same substituents on both the P(III) and P(V) compounds. The uniqueness of the pentacoordinated systems may be appreciated when we recognize that, in both tetracoordinated and hexacoordinated phosphorus6,15 (and arsenic31) compounds, this 1,3,2-dioxaphosphorinane (or 1,3,2-dioxarsenane) ring has a chair conformation. A similar change in conformation from boat-chair in phosphites to tub in phosphoranes is demonstrated for the first time in systems containing the 1,3,2-dioxaphosphocin ring. A generalization that this ring prefers the tub conformation when it is positioned apical-equatorially (three structures) and boat-chair when it is diequatorial (five structures) in a trigonal bipyramidal geometry can, perhaps, be made on the basis of available structures. Acknowledgment. Financial support by the Council of Scientific and Industrial Research (New Delhi, India) is gratefully acknowledged. Thanks are also due to UGC, India (COSIST and Special Assistance Programme), as well as AvH Foundation (Germany) for instrumental facilities. We are thankful to Prof. Dr. G. M. Sheldrick for his interest in this work. Supporting Information Available: Analytical and spectroscopic data for 10-12 and data pertaining to identification of 16-20; atomic coordinates, isotropic displacement parameters, complete listing of bond lengths and angles, and anisotropic displacement parameters for structures of 1-4 (20 pages). Four X-ray crystallographic files, in CIF format, are available on the Internet only. Access and ordering information is given on any current masthead page. IC9611958 (31) Said, M. A.; Kumara Swamy, K. C.; Veith, M.; Huch, V. Inorg. Chem. 1996, 35, 6627.